How can I show custom page when publishing my web site?

We all know when we want to upload new dll files and upgrade our web application, web get this error when opening the website:

Server Error in '/' Application.

Could not load file or assembly '****' or one of its dependencies. The process cannot access the file because it is being used by another process. (Exception from HRESULT: 0x80070020)

I'm looking for a solution to handle this error and show a custom html file when dll is uploading.

Any Idea?!

Before you start uploading DLLs, upload an app_offline.html file to the root of the web application. You can customize this however you see fit.

Remove it when your done updating your DLL files.